Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.84	9.515%	$110.4349	$110.43	$110.45	$110.40
Purchase #2	$217.88	10.516%	$240.7923	$240.79	$240.80	$240.80
Purchase #3	$109.55	5.776%	$115.8776	$115.88	$115.90	$115.90
Purchase #4	$222.63	5.163%	$234.1244	$234.12	$234.10	$234.10
Purchase #5	$152.42	6.508%	$162.3395	$162.34	$162.35	$162.30
Purchase #6	$152.39	4.555%	$159.3314	$159.33	$159.35	$159.30
Purchase #7	$55.52	6.360%	$59.0511	$59.05	$59.05	$59.10
7 purchase totals =	$1,011.23		$1,081.9512	$1,081.94	$1,082.00	$1,081.90